The exemplary embodiment relates to lubricant additives and in particular to protected mercaptophenols useful in lubricating compositions.
Thermal and mechanical stresses on lubricants, such as engine and driveline oils, tend to increase the tendency towards formation of deposits on the lubricated components, such as internal combustion engines and driveline components. This can negatively impact the performance of the lubricated components through reduction in engine efficiency or overall life-expectancy. Such lubricants generally incorporate, in addition to a base oil, a number of additives, including friction modifiers, antiwear agents, antioxidants, dispersants, and detergents, that are used to protect lubricated components from wear, oxidation, soot deposits, corrosion, acid build up, and the like, and to improve water tolerance and compatibility of formulation components.
Dispersants are used for dispersing impurities such as wear particles, soot and other contaminants. Amine-based dispersants, such as polyamine succinimides, have been widely used. These dispersants often have basic functionality which can help to neutralize acidic contaminants. However, they have a tendency to reduce corrosion protection and seals compatibility.
Salicylate and catecholate additives have been used to provide desirable performance attributes to lubricant formulations, including cleanliness, antioxidancy, and dispersancy.
Branched para-C12-alkylphenols, including p-dodecylphenol (PDDP) also known as tetrapropenylphenol (TPP), formed from tetrapropene have seen extensive commercial use as chemical intermediates in the production of oil and lubricant additives for gasoline and diesel-powered engines. Recently, however, some countries have placed limits on the amount PDDP that is considered acceptable. Therefore it is desirable to develop an alternative to PDDP and other alkylphenols for use as detergents.
There have been several efforts to prepare detergents that do not contain alkyl phenols derived from oligomers of propylene. These include U.S. Pub. Nos. 2008/0269351, 2011/0118160, 2011/0124539, 2011/0190185, 2010/0029529 and WO 2013/059173. Other compounds are disclosed in U.S. Pat. Nos. 6,310,009, 6,235,688, 5,510,043, 4,221,673, 4,643,838, 4,729,848, 4,058,472, 3,816,353, 3,864,286, 4,058,472, 3,816,353, 3,864,286, and U.S. Pub. Nos. 2007/0049508, 255/0288194, 2004/077507, 2014/130767, WO 2014/033323, and EP 2374866 A1.